Method and apparatus for handover and session continuity using pre-registration tunneling procedure

ABSTRACT

A method and apparatus for session continuity using pre-registration tunneling procedure are disclosed. For session continuity, a tunnel is established between a multi-mode wireless transmit/receive unit (WTRU) and a core network of a target system via a source system while the WTRU is still connected with the source system. An access procedure is performed toward the target system using the tunnel. A handover is the performed from the source system to the target system once the access procedure is complete. The access procedure includes session initiation protocol (SIP) registration, authentication of the WTRU at the target system, and internet protocol (IP) configuration. The handover may be from a third generation partnership project (3GPP) system to a non-3GPP system, or vice versa.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application Nos.60/948,587 filed on Jul. 9, 2007 and 60/949,085 filed on Jul. 11, 2007,which are incorporated by reference as if fully set forth.

FIELD OF INVENTION

The present application is related to wireless communication systems.

BACKGROUND

A dual-mode or multi-mode wireless transmit/receive unit has dual ormultiple radio transceivers, each designed to communicate on aparticular radio access technology (RAT), such as 3^(rd) GenerationPartnership Project (3GPP) and non-3GPP systems. The handover processbetween 3GPP and non-3GPP systems may be slow due to the nature of thesystem configurations and operations. One problem occurs when a WTRUmoves from one system to another as the WTRU is required to register andauthenticate in the other system. A similar problem exists for sessioninitiation protocol (SIP)-based Session Continuity processes between3GPP and non-3GPP systems. When moving from one system to the other, theWTRU is required to register and authenticate in the other system beforeregistering with internet protocol (IP) multimedia subsystem (IMS).

Another problem may occur due to the 3GPP prohibition againstsimultaneous radio transceiver operation. A single WTRU cannot have a3GPP radio transceiver and a non-3GPP radio transceiver active at thesame time. In such cases, dual-mode or multi-mode radio transceiversneed sophisticated control of the radio switching.

SUMMARY

The present invention is related to a method and apparatus for sessioncontinuity using pre-registration tunneling procedure. For sessioncontinuity, a tunnel is established between a wireless transmit/receiveunit (WTRU) and a core network of a target system via a source systemwhile the WTRU is still connected with the source system. An accessprocedure is performed toward the target system using the tunnel. Ahandover is performed from the source system to the target system oncethe access procedure is complete. For session initiation protocol (SIP)based handover, the access procedure includes SIP registration,authentication of the WTRU at the target system, and internet protocol(IP) configuration. The handover may be from a third generationpartnership project (3GPP) system to a non-3GPP system, or vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding of the invention may be had from thefollowing description of a preferred embodiment, given by way of exampleand to be understood in conjunction with the accompanying drawingswherein:

FIG. 1 shows a block diagram of dual protocol stack configuration in adual mode wireless transmit/receive unit (WTRU) in accordance with afirst embodiment;

FIG. 2 shows a block diagram of a dual protocol stack configuration in adual mode WTRU supporting pre-registration SIP-based session continuityin accordance with a second embodiment;

FIGS. 3A and 3B show a signal diagram of a pre-registration procedurefor a 3GPP to non-3GPP handover in accordance with the first embodiment;

FIGS. 4A and 4B show a signal diagram of a pre-registration procedurefor a non-3GPP to 3GPP handover in accordance with the first embodiment;

FIGS. 5A, 5B and 5C show a signaling diagram of pre-registrationprocedures for 3GPP to non-3GPP handover in accordance with the secondembodiment;

FIGS. 6A, 6B and 6C show a signaling diagram of pre-registrationprocedures for non-3GPP to 3GPP handover in accordance with the secondembodiment;

FIG. 7 shows dual stack operation in a multi-mode WTRU supportingpre-registration SIP-based session continuity for 3GPP to non-3GPPhandover in accordance with the second embodiment; and

FIG. 8 shows dual stack operation in a multi-mode WTRU supportingpre-registration SIP-based session continuity for non-3GPP to 3GPPhandover in accordance with the second embodiment.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “WTRU” includes but is notlimited to a user equipment (UE), a mobile station, a fixed or mobilesubscriber unit, a pager, a cellular telephone, a personal digitalassistant (PDA), a computer, or any other type of user device capable ofoperating in a wireless environment. When referred to hereafter, theterminology “base station” includes but is not limited to a Node-B, asite controller, an access point (AP), or any other type of interfacingdevice capable of operating in a wireless environment.

By way of reference, as a WTRU moves from a system A to a system B,system A is defined as the handover source and system B is defined asthe handover target. One mechanism to speed access procedures to atarget system is to allow pre-registration and pre-authenticationprocedures to be performed by upper layers in a WTRU via the sourcesystem. The source system may identify the target system, establish atunnel between the WTRU and the core target network, (e.g., AutonomousRegistration (AR) or Access, Authentication and Accounting (AAA)), andinstruct the WTRU to start access procedures for the target network.Upon successful completion of the access procedure, the source networkmay instruct the WTRU to switch, or handover, to the target network andturn off the radio connected to the source network.

FIG. 1 is a block diagram of dual protocol layer stack in a dual modeWTRU 101 supporting pre-registration tunneling in accordance with afirst embodiment. As shown in FIG. 1, the WTRU 101 includes a non-3GPPprotocol layer stack comprising an application layer 110, a mobilitymanagement (MM) layer 111, a radio resource control (RRC) and mediaaccess control (MAC) layer 112, and a physical (PHY) layer 113. Theapplication layer 110 is coupled to the MM layer 111 by path 115. The MMlayer 111 is coupled to the RRC/MAC layer 112 by path 116. Path 117couples the RRC/MAC layer 112 to the PHY layer 113. Similarly, a 3GPPprotocol layer stack comprises an application layer 120, a multimedia(MM) layer 121, a radio resource control (RRC) and media access control(MAC) layer 122, and a physical (PHY) layer 123. The application layer120 is coupled to the MM layer 121 by path 125. The MM layer 121 iscoupled to the RRC/MAC layer 122 by path 126. Path 127 couples theRRC/MAC layer 122 to the PHY layer 123.

The dual protocol layer stack is further configured to include a path141, which cross connects the non-3GPP PHY layer 113 to the 3GPP RRC/MAClayer 122. A path 131 couples the 3GPP PHY layer 123 to the non-3GPPRRC/MAC layer 112. These paths 131 and 141 are used to establishtunneling between 3GPP and non-3GPP systems to facilitate 3GPP tonon-3GPP handover. A controller 151 controls the signaling for handoverand access procedures executed at the protocol stack layers shown inFIG. 1.

FIG. 2 is a block diagram of dual protocol layer stack in a dual modeWTRU 201 supporting pre-registration tunneling in accordance with asecond embodiment. As shown in FIG. 2, the WTRU 201 includes a non-3GPPprotocol layer stack comprising an application layer 210, a sessionmanagement (SM) and mobility management (MM) layer 211, a radio resourcecontrol (RRC) and media access control (MAC) layer 212, and a physical(PHY) layer 213. The application layer 210 is coupled to the SM and MMlayer 211 by path 215. The SM and MM layer 211 is coupled to the RRC/MAClayer 212 by path 216. Path 217 couples the RRC/MAC layer 212 to the PHYlayer 213. Similarly, a 3GPP protocol layer stack comprises anapplication layer 220, a SM and MM layer 221, a radio resource control(RRC) and media access control (MAC) layer 222, and a physical (PHY)layer 223. The application layer 220 is coupled to the SM and MM layer221 by path 225. The SM and MM layer 221 is coupled to the RRC/MAC layer222 by path 226. Path 227 couples the RRC/MAC layer 222 to the PHY layer223.

The dual protocol layer stack is further configured to include a path241, which cross connects the non-3GPP PHY layer 213 to the 3GPP RRC/MAClayer 222. A path 231 couples the 3GPP PHY layer 223 to the non-3GPPRRC/MAC layer 212. These paths 231 and 241 are used to establishtunneling between 3GPP and non-3GPP systems to facilitate 3GPP tonon-3GPP handover. A controller 251 controls the signaling for handoverand access procedures executed at the protocol stack layers shown inFIG. 2.

FIGS. 3A and 3B show a signal diagram for pre-registration procedure fora handover of a WTRU 301 from a 3GPP handover source 304 to a non-3GPPhandover target 305. A WTRU 301 includes a 3GPP radio transceiver 302and a non-3GPP radio transceiver 303 for communication with a 3GPP corenetwork (CN) 304 and a non-3GPP CN 305. For simplicity, a dual mode WTRU301 is shown, however the signaling described herein is valid for amulti-mode WTRU having multiple 3GPP and non-3GPP radio transceivers.While shown as direct signals from the WTRU 301 and CNs 303, 304, thesignals may be relayed by a NodeB or a base station entity (not shown).

The pre-registration begins with the 3GPP transceiver 302 receiving a3GPP and non-3GPP measurement list 311 from 3GPP CN 304. The measurementlist 311 identifies the channel frequencies of candidate handovertargets. At 312, the WTRU 301 stores the list in an internal memory, andfor periodically initiating channel measurements. The 3GPP transceiver302 sends an initialization signal 313 to the non-3GPP transceiver 303,along with a list of candidate non-3GPP handover targets 314. At 315,the non-3GPP transceiver 303 is activated for a period in order toperform measurement procedures, in which it monitors channels andperforms measurements. The non-3GPP transceiver 303 sends measurementreports 316 of the monitored channels to the 3GPP transceiver 302. Whenmeasurement procedures by the non-3GPP transceiver 303 are completed, itmay be deactivated.

At 317, the 3GPP transceiver 302 combines the measurements it made withthose made by the non-3GPP transceiver 303, formulates combinedmeasurement reports, and transmits the combined measurement reports tothe 3GPP CN 304. At 318, the 3GPP CN 304 examines the combinedmeasurement reports and handover (HO) criteria, and selects a handovertarget system for the WTRU 301. The 3GPP CN 304 sends a signal 319 tothe target non-3GPP CN 305 to initiate a handover direct tunnel, and thetarget non-3GPP CN 305 responds with a tunnel establishmentacknowledgment signal 320. The 3GPP CN 304 sends a signal 321 to the3GPP transceiver 302 to initiate a handover direct tunnel. This signal321 may include a non-3GPP tunnel endpoint identification (TEID). The3GPP transceiver 302 sends the target ID 322 to the non-3GPP transceiver303. The non-3GPP transceiver sends its handover direct tunnelacknowledgment (ACK) 323 to the 3GPP transceiver 302, which is thenforwarded to the 3GPP CN 304 as signal 324. The direct handover tunnel325 is established between the non-3GPP target CN 305 and the non-3GPPtransceiver 303. The source 3GPP CN 304 sends a signal 326 to initiate anon-3GPP registration to the 3GPP transceiver 302 which is thenforwarded as signal 327 to the non-3GPP transceiver 303. The upperlayers of the non-3GPP transceiver 303 perform pre-registrationpre-authentication procedures, and send a non-3GPP registration request328, 329 via the 3GPP transceiver 302 to the non-3GPP target CN 305.

The 3GPP radio transceiver 302 and the non-3GPP target CN 305 thenconduct authentication procedures 330. Handover triggers 331 arecommunicated directly between the 3GPP CN 304 and non-3GPP CN 305 andthe 3GPP CN 304 initiates handover with a signal 332 to the 3GPPtransceiver 302. The 3GPP transceiver 302 instructs the non-3GPP radiotransceiver 303 to turn ON as signal 333. With the non-3GPP radiotransceiver 303 turned ON, it makes initial contact with the non-3GPP CN305 and commences radio contact procedures 334. The 3GPP radiotransceiver 302 is turned OFF at 335 and the 3GPP CN 304 and non-3GPP CN305 exchange handover complete and tunnel release signals 336.

FIG. 4 is a signal diagram for pre-registration procedure for a handoverof a WTRU 401 from a non-3GPP handover source 404 to a 3GPP handovertarget 405. A WTRU 401 includes a non-3GPP radio transceiver 402 and a3GPP radio transceiver 403 for communication with a non-3GPP corenetwork (CN) 404 and a 3GPP CN 405. For simplicity, a dual mode WTRU 401is shown, however the signaling described herein is valid for amulti-mode WTRU having multiple 3GPP and non-3GPP radio transceivers.While shown as direct signals between the WTRU 401 and CNs 403, 404, thesignals may be relayed by a NodeB or a base station entity (not shown).The pre-registration begins with the non-3GPP transceiver 402 receivinga 3GPP and non-3GPP measurement list 411 from non-3GPP CN 404. Themeasurement list 411 identifies the channel frequencies of candidatehandover targets. At 412, the WTRU 401 stores the list in an internalmemory, and for periodically initiating channel measurements. Thenon-3GPP transceiver 402 sends an initialization signal 413 to the 3GPPtransceiver 403, along with a list of candidate 3GPP handover targets414. The 3GPP transceiver 403 is activated and monitors channels andperforms measurements at 415.

The 3GPP transceiver 403 sends measurement reports 416 of the monitoredchannels to the non-3GPP transceiver 402. The non-3GPP transceiver 402combines the measurements it made with those made by the 3GPPtransceiver 403, formulates combined measurement reports, and transmitsthe combined measurement reports 417 to the non-3GPP CN 404. At 418, thenon-3GPP CN 404 examines the combined measurement reports and selects ahandover target system for the WTRU 401. The non-3GPP CN 404 sends asignal 419 to the target 3GPP CN 405 to initiate a handover directtunnel, and the target 3GPP CN 405 responds with a tunnel establishmentacknowledgment signal 420. The 3GPP non-CN 404 sends a signal 421 to thenon-3GPP transceiver 402 to initiate a handover direct tunnel. Thissignal 421 may include a 3GPP tunnel endpoint identification (TEID). Thenon-3GPP transceiver 402 sends the target ID 422 to the 3GPP transceiver403. The 3GPP transceiver sends its handover direct tunnelacknowledgment (ACK) 423 to the non-3GPP transceiver 402, which is thenforwarded to the non-3GPP CN 404 as signal 424. The direct handovertunnel 425 is established between the 3GPP target CN 405 and the 3GPPtransceiver 403. The source non-3GPP CN 404 sends a signal 426 toinitiate a 3GPP registration to the non-3GPP transceiver 402 which isthen forwarded as signal 427 to the 3GPP transceiver 403. A 3GPPregistration request 428,429 is sent from the 3GPP transceiver 403 viathe non-3GPP transceiver 402 to the 3GPP target CN 405.

The non-3GPP radio transceiver 402 and the 3GPP target CN 405 thenconduct authentication procedures 430. Handover triggers 431 arecommunicated directly between the non-3GPP CN 404 and 3GPP CN 405 andthe non-3GPP CN 404 initiates handover with a signal 432 to the non-3GPPtransceiver 402. The non-3GPP transceiver 402 instructs the non-3GPPradio transceiver 403 to turn ON with signal 433. With the 3GPP radiotransceiver 403 turned ON, it makes initial contact with the 3GPP CN 405and commences radio contact procedures 434. The non-3GPP radiotransceiver 402 is turned OFF at 435 and the non-3GPP CN 404 and 3GPP CN405 exchange handover complete and tunnel release signals 436.

FIGS. 5A, 5B and 5C show a signaling diagram of an SIP-based handover ofa dual-mode WTRU 501 from a 3GPP source system to a non-3GPP targetsystem. In order to speed the access procedures and hence the handoverto the target system, pre-registration and pre-authentication proceduresare allowed to be performed by the upper layers in the WTRU 501 of thetarget technology via the source system, including the IP configurationand connectivity establishment, and the SIP registration andconnectivity establishment.

In FIG. 5A, the WTRU 501 comprises a 3GPP radio transceiver 502 and anon-3GPP radio transceiver 503. Also shown are a 3GPP source CN 504 anda non-3GPP target CN 505. The core networks CN 504 and 505 may beimplemented as an access router (AR), access service network (ASN), orauthentication, authorization and accounting (AAA) entity. The non-3GPPtarget system may include for example 3GPP2, WiMAX, or WiFi.

As shown in FIG. 5A, SIP connectivity 511 is already established betweenthe 3GPP transceiver 502 and the 3GPP CN 504 and SIP connectivity 512 isalready established between the 3GPP CN 504 and the internet protocol(IP) multimedia server (IMS) 506. The pre-registration begins with the3GPP transceiver 502 receiving a 3GPP and non-3GPP measurement list 513from 3GPP CN 504. The measurement list 513 identifies the channelfrequencies of candidate handover targets. At 514, the WTRU 501 storesthe list in an internal memory, and for use in periodically initiatingchannel measurements. The 3GPP transceiver 502 sends an initializationsignal 515 to the non-3GPP transceiver 503, along with a list ofcandidate non-3GPP handover targets 516. At 517, the non-3GPPtransceiver 503 monitors channels and performs measurements.

The non-3GPP transceiver 503 sends measurement reports 518 of themonitored channels to the 3GPP transceiver 502. The 3GPP transceiver 502combines the measurements it made with those made by the non-3GPPtransceiver 503, formulates combined measurement reports, and transmitsthe combined measurement reports 519 to the 3GPP CN 504. At 520, the3GPP CN 504 examines the combined measurement reports and selects ahandover target system for the WTRU 501. The 3GPP CN 504 sends a signal521 (FIG. 5B) to the target non-3GPP CN 505 to initiate a handoverdirect tunnel, and the target non-3GPP CN 505 responds with a tunnelestablishment acknowledgment signal 522. The 3GPP CN 504 sends a signal523 to the 3GPP transceiver 502 to initiate a handover direct tunnel.This signal 523 may include a non-3GPP tunnel endpoint identification(TEID). The 3GPP transceiver 502 sends the target ID 524 to the non-3GPPtransceiver 503. The non-3GPP transceiver sends its handover directtunnel acknowledgment (ACK) 525 to the 3GPP transceiver 502, which isthen forwarded to the 3GPP CN 504 as signal 526. The direct handovertunnel 527 is established between the non-3GPP target CN 505 and thenon-3GPP transceiver 503. The source 3GPP CN 504 sends a signal 528 toinitiate a non-3GPP registration to the 3GPP transceiver 502 which isthen forwarded as signal 529 to the non-3GPP transceiver 503. A non-3GPPregistration request 529A is sent from the non-3GPP transceiver 503 tothe 3GPP transceiver 502, and forwarded as signal 530 to the non-3GPPtarget CN 505. The registration request 529A, 530 may include the TEIDof the target CN 505.

The 3GPP radio transceiver 502 and the non-3GPP target CN 505 thenconduct authentication procedures 531. Signaling 532 occurs betweendifferent protocol stack layers of the 3GPP radio transceiver 502 andthe non-3GPP transceiver 503, where authorization information isexchanged to update the status of the protocol. If successful, then theprocess of establishing IP connection commences at 533. The signaling534 between the WTRU radio transceivers 502, 503 for establishing IPconnectivity is started by tunneling the non-3GPP IP configurationmessage to the 3GPP protocol stack along crossover path 241.

The 3GPP transceiver 502 establishes non-3GPP IP configurationprocedures 535 with the non-3GPP CN 505. IP configuration messages 536,537 are exchanged between the 3GPP transceiver 502 and the non-3GPPtransceiver 503, which may include the IP address of the IP gateway, IPtype (e.g., IPv4 or IPv6) and the corresponding quality of signal (QoS)parameters. Additional information may also be sent in the signals 536,537, including a list of Proxy Call State Control Function (P-CSCF) tosupport the non-3GPP radio transceiver 503 to configure its SIPconnectivity. The IP configuration of the non-3GPP transceiver iscomplete at 538.

For a handover between a 3GPP system and a non-3GPP system, twodifferent IP gateways are involved. One IP gateway is for 3GPP, which isconnecting the IMS to the 3GPP transceiver 502, and the other IP gatewayis for establishing the IP connectivity over a non-3GPP system for thenon-3GPP transceiver 503.

As shown in FIG. 5C, the SIP based handover signaling continues at 540,where the non-3GPP transceiver 503 commences SIP registrationprocedures. Signals 541-544 are used to exchange SIP addresses and toperform P-CSCF discovery for connecting the SIP layer in the non-3GPPtransceiver 503 to the IMS 506 via the Non-3GPP Core network. Signal 541is exchanged between the 3GPP transceiver 502 and the non-3GPPtransceiver 503 using the crossover path 241. Signal 542 is sent overthe 3GPP air interface from the 3GPP transceiver 602 PHY layer. Signal543 is exchanged between the 3GPP CN 504 and the non-3GPP CN 505 andsignal 544 is exchanged between the non-3GPP CN 505 and the IMS 506.Acknowledgment signals 545 and 546 are sent between the appropriateprotocol layer in the Non-3GPP transceiver 503 and the 3GPP transceiver502 upon successful SIP registration.

With the SIP registration of the non-3GPP transceiver 503 complete at547, SIP connectivity 548 and 549 is established between the non-3GPPtransceiver 503 and the non-3GPP CN 505, and between the non-3GPP CN 505and the IMS 506, respectively. The non-3GPP CN 505 informs the 3GPP CN504 that handover is complete with signal 550. The 3GPP transceiver 502then performs SIP deregistration and IP release procedures 551 with theIMS 506. The 3GPP transceiver 502 receives signal 552 from the 3GPP CN504 indicating a handover complete, a radio switch OFF command and arelease 3GPP radio access bearer (RAB) command. The 3GPP transceiver 502informs the non-3GPP transceiver 503 that the handover is complete withsignal 553, and the non-3GPP radio transceiver 503 is activated ON. At554, the non-3GPP transceiver 503 commences non-3GPP RF connectivityprocedures with the non-3GPP CN 505.

FIGS. 6A, 6B and 6C show a signaling diagram of an SIP-based handover ofa dual-mode WTRU 601 from a non-3GPP source system to a 3GPP targetsystem. In order to speed the access procedures and hence the handoverto the target system, pre-registration and pre-authentication proceduresare allowed to be performed by the upper layers in the WTRU 601 of thetarget technology via the source system, including the IP configurationand the SIP registration procedures.

In FIG. 6A, the WTRU 601 comprises a 3GPP radio transceiver 602 and anon-3GPP radio transceiver 603. Also shown are a 3GPP target CN 604 anda non-3GPP source CN 605. The core networks CN 604 and 605 may beimplemented as an access router (AR), access service network (ASN), orauthentication, authorization and accounting (AAA) entity. The non-3GPPtarget system may include for example 3GPP2, WiMAX, or WiFi.

As shown in FIG. 6A, SIP connectivity 611 is already established betweenthe non-3GPP transceiver 603 and the non-3GPP CN 605 and SIPconnectivity 612 is already established between the non-3GPP CN 604 andthe IP multimedia server (IMS) 606. The pre-registration begins with the3GPP transceiver 603 receiving a 3GPP and non-3GPP measurement list 613from non-3GPP CN 605. The measurement list 613 identifies the channelfrequencies of candidate handover targets. At 614, the WTRU 601 storesthe list in an internal memory, and for use in periodically initiatingchannel measurements. The non-3GPP transceiver 603 sends aninitialization signal 615 to the 3GPP transceiver 602, along with a listof candidate 3GPP handover targets 616. At 617, the 3GPP transceiver 602monitors channels and performs measurements.

The 3GPP transceiver 602 sends measurement reports 618 of the monitoredchannels to the non-3GPP transceiver 603. The non-3GPP transceiver 603combines the measurements it made with those made by the 3GPPtransceiver 603, formulates combined measurement reports, and transmitsthe combined measurement reports 619 to the non-3GPP CN 605. At 620, thenon-3GPP CN 605 examines the combined measurement reports and selects ahandover target system for the WTRU 601. The non-3GPP CN 605 sends asignal 621 (FIG. 6B) to the target 3GPP CN 604 to initiate a handoverdirect tunnel, and the target 3GPP CN 604 responds with a tunnelestablishment acknowledgment signal 622. The non-3GPP CN 605 sends asignal 623 to the non-3GPP transceiver 603 to initiate a handover directtunnel. This signal 623 may include a 3GPP tunnel endpointidentification (TEID). The non-3GPP transceiver 603 sends the target ID624 to the 3GPP transceiver 602. The 3GPP transceiver 602 sends itshandover direct tunnel acknowledgment (ACK) 625 to the non-3GPPtransceiver 603, which is then forwarded to the non-3GPP CN 605 assignal 626. The direct handover tunnel 627 is established between the3GPP target CN 604 and the 3GPP transceiver 602. The source non-3GPP CN605 sends a signal 628 to initiate a 3GPP registration to the non-3GPPtransceiver 603 which is then forwarded as signal 629 to the 3GPPtransceiver 602. A 3GPP registration request 629A is sent from the 3GPPtransceiver 602 to the non-3GPP transceiver 603 and forwarded as signal630 to the 3GPP target CN 604. The registration request 629A, 630 mayinclude the TEID of the target CN 604.

The non-3GPP radio transceiver 603 and the 3GPP target CN 604 thenconduct authentication procedures 631. Signaling 632 occurs betweendifferent protocol stack layers of the 3GPP radio transceiver 602 andthe non-3GPP transceiver 603, where authorization information isexchanged to update the status of the protocol. If successful, then theprocess of establishing IP connection commences at 633. The signaling634 for IP connectivity is started by tunneling the 3GPP IPconfiguration message to the non-3GPP protocol stack along crossoverpath 231.

The non-3GPP transceiver 603 establishes 3GPP IP configurationprocedures 635 with the 3GPP CN 604. IP configuration messages 636, 637are exchanged between the 3GPP transceiver 602 and the non-3GPPtransceiver 603, which may include the IP address of the IP gateway, IPtype (e.g., IPv4 or IPv6) and the corresponding quality of signal (QoS)parameters. Additional information may also be sent in the signals 636,637, including a list of Proxy Call State Control Function (P-CSCF) tosupport the 3GPP radio transceiver 602 to configure its SIPconnectivity. The IP configuration of the non-3GPP transceiver iscomplete at 638.

As shown in FIG. 6C, the SIP based handover signaling continues at 640,where the 3GPP transceiver 602 commences SIP registration procedures.Signals 641-644 are used to exchange SIP addresses and to perform P-CSCFdiscovery for connecting the SIP layer in the 3GPP transceiver 602 tothe IMS 606 via the 3GPP core network 604. Signal 641 is exchangedbetween the 3GPP transceiver 602 upper layers and the non-3GPPtransceiver 603 PHY layer using the crossover path 231. Signal 642 issent over the non-3GPP air interface from the non-3GPP transceiver 603PHY layer to the non-3GPP CN 605. Signal 643 is exchanged between thenon-3GPP CN 605 and the 3GPP CN 604 and signal 644 is exchanged betweenthe 3GPP CN 604 and the IMS 606. Acknowledgment signals 645 and 646 aresent between the appropriate protocol layer in the Non-3GPP transceiver603 and the 3GPP transceiver 602 upon successful SIP registration.

With the SIP registration of the 3GPP transceiver 602 complete at 647,SIP connectivity 648 and 649 is established between the 3GPP transceiver602 and the 3GPP CN 604, and between the 3GPP CN 604 and the IMS 606,respectively. The 3GPP CN 604 informs the non-3GPP CN 605 that handoveris complete with signal 650. The non-3GPP transceiver 603 then performsSIP deregistration and IP release procedures 651 with the IMS 606. Thenon-3GPP transceiver 603 receives signal 652 from the non-3GPP CN 605indicating a handover complete, a radio switch OFF command and a releasenon-3GPP radio access bearer (RAB) command. The non-3GPP transceiver 603informs the 3GPP transceiver 602 that the handover is complete withsignal 653, and the 3GPP radio transceiver 602 is activated ON. At 654,the 3GPP transceiver 602 commences 3GPP RF connectivity procedures withthe 3GPP CN 604.

FIGS. 7 and 8 show systematic block diagrams for the SIP based handovermethod described above. In FIG. 7, communication links for a handover ofWTRU 201 from a 3GPP source system to a non-3GPP target system is shownsequentially by signal paths 701, 702 and 703. Initially, the WTRU 201is connected to the 3GPP source system on signal path 701 via an IMS711, a 3GPP CN 721, and a 3GPP eNodeB (eNB) 722 that is in a wirelesscommunication with the 3GPP PHY layer 223. In order to prepare forhandover to a non-3GPP target, a make-before-break path 702 isestablished to the non-3GPP transceiver protocol stack (i.e., SIPapplication layer 210, SM and MM layer 211, RRC and MAC layer 212) viathe crossover path 241 between the 3GPP PHY layer 223 and non-3GPP RRCand MAC layer 212. The communication path 702 allows the non-3GPPprotocol stack to receive target system information via the active 3GPPsource system using the 3GPP eNB 722, the 3GPP CN 721, which exchangesinformation with the target non-3GPP CN 731, gateway (GW) 712 and IMS711. The communication path 702 is established when the WTRU 201receives instructions from the source 3GPP system to start the accessprocedures toward the target system and to perform the sequence ofaccess specific procedures (e.g., Attach, IP configuration, and SIPRegistration). Upon successful completion of the access specificprocedures and the SIP registration, the SIP connectivity is establishedas shown by communication path 703 between the non-3GPP protocol stack(i.e. layers 210, 211, 212 and PHY layer 213) and the non-3GPP radioaccess network (RAN) 732, the non-3GPP CN 731, the gateway (GW) 712 andIMS 711. The WTRU 201 receives instructions from the 3GPP source systemto switch (or handover) to the non-3GPP target system and turn off theradio on the 3GPP source system (i.e., turn OFF the 3GPP transceiver ofWTRU 201), which terminates the communication links 701 and 702. Thisensures that the SIP based session is established to the non-3GPP targetsystem. A WTRU controller 251 executes the access procedures and thehandover procedures responsive to the received instructions from the3GPP source system.

In FIG. 8, communication links for a handover of WTRU 201 from anon-3GPP source system to a 3GPP target system is shown sequentially bysignal paths 801, 802 and 803. Initially, the WTRU 201 is connected tothe non-3GPP source system on signal path 801 via an IMS 711, a gateway(GW) 712, a non-3GPP CN 731, and a non-3GPP RAN 732 that is in awireless communication with the non-3GPP PHY layer 213. In order toprepare for handover to a 3GPP target system, a make-before-break path802 is established between 3GPP target system to the 3GPP transceiverprotocol stack (i.e., SIP application layer 220, SM and MM layer 221,RRC and MAC layer 222) via the crossover path 231 between the non-3GPPPHY layer 213 and non-3GPP RRC and MAC layer 222. The communication path802 allows the 3GPP protocol stack to receive target system informationvia the active non-3GPP source system using the non-3GPP RAN 732, thenon-3GPP CN 731, which exchanges information with the target 3GPP CN 721and IMS 711. The communication path 802 is established when the WTRU 201receives instructions from the source non-3GPP system to start theaccess procedures toward the 3GPP target system and to perform thesequence of access specific procedures (e.g., Attach, IP configuration,and SIP Registration). Upon successful completion of the access specificprocedures and the SIP registration, the SIP connectivity is establishedas shown by communication path 803 between the 3GPP protocol stack (i.e.layers 220, 221, 222 and PHY layer 223) and the non-3GPP RAN 732,followed by the non-3GPP CN 731, the 3GPP CN 721 and IMS 711. The WTRU201 receives instructions from the 3GPP source system to switch (orhandover) to the non-3GPP target system and turn off the radio on the3GPP source system (i.e., turn OFF the non-3GPP transceiver of WTRU201), which terminates the communication links 801 and 802. This ensuresthat the SIP based session is established to the non-3GPP target system.A WTRU controller 251 executes the access procedures and the handoverprocedures responsive to the received instructions from the 3GPP sourcesystem.

Although the features and elements of the present invention aredescribed in the preferred embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the preferred embodiments or in various combinations with orwithout other features and elements of the present invention. Themethods or flow charts provided in the present invention may beimplemented in a computer program, software, or firmware tangiblyembodied in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) module.

1. A method for handover of a wireless transmit receive unit (WTRU) froma source system to a target system, the method comprising: establishinga tunnel between the WTRU and a core network (CN) of the target systemvia a first radio transceiver, wherein data communicated via the tunnelreceived on a physical (PHY) layer of the first radio transceiver istransferred to at least one of a radio resource control layer or a mediaaccess control layer of a second radio transceiver using a crossoverconnection between the first radio transceiver and the second radiotransceiver, the first radio transceiver being configured to communicateon a radio access technology (RAT) of the source system and the secondradio transceiver being configured to communicate on a RAT of the targetsystem; performing an access procedure with the CN of the target systemusing the tunnel; and establishing communications with the target systemvia the second transceiver on the RAT of the target system uponsuccessful completion of the access procedure with the CN of the targetsystem performed via the tunnel.
 2. The method as in claim 1, whereinthe access procedure is an attach procedure.
 3. The method as in claim1, further comprising the WTRU receiving a message from the sourcesystem instructing the WTRU to initiate the access procedure toward thetarget system.
 4. The method of claim 1, wherein the access procedure isa session initiation protocol (SIP) registration procedure resulting inSIP connectivity with the target system.
 5. The method as in claim 1,wherein the access procedure includes authentication of the WTRU at thetarget system.
 6. The method as in claim 1, wherein the access procedureincludes packet data protocol (PDP) context activation.
 7. The method asin claim 1, wherein the access procedure includes establishing internetprotocol (IP) connectivity to the target system.
 8. The method as inclaim 1, wherein the access procedure is at least one of apre-registration procedure or a pre-authentication procedure.
 9. Themethod of claim 1, further comprising receiving a message from thesource system requesting establishment of the tunnel, wherein themessage includes a tunnel endpoint identification (TEID) identifying anendpoint of the tunnel in the of the target system.
 10. The method as inclaim 1, further comprising the second transceiver performingmeasurements of the target system.
 11. The method as in claim 10,further comprising the first transceiver sending a measurement report tothe source system, wherein the measurement report comprises themeasurements of the target system performed by the second transceiver.12. The method as in claim 1, wherein the source system is a 3rdGeneration Partners Project (3GPP) system and the target system is anon-3GPP system.
 13. The method as in claim 1, wherein the source systemis a non-3rd Generation Partnership Project (3GPP) system and the targetsystem is a 3GPP system.
 14. The method as in claim 1, wherein theaccess procedure is at least one of a pre-registration procedure or apre-authentication procedure.
 15. A wireless transmit/receive unit(WTRU) comprising: a first radio transceiver configured for wirelesscommunication on a radio access technology (RAT) of a source system; asecond radio transceiver configured for wireless communication on aradio access technology (RAT) of a target system; and a controllerconfigured to: establish a tunnel between the WTRU and a core network(CN) of the target system via the first radio transceiver while the WTRUis still connected with the source system, wherein data communicated viathe tunnel received on a physical (PHY) layer of the first radiotransceiver is transferred to at least one of a radio resource controllayer or a media access control layer of the second radio transceiver,perform an access procedure with the CN of the target system using thetunnel, and establish communications with the target system via thesecond transceiver on the RAT of the target system upon successfulcompletion of the access procedure with the CN of the target systemperformed using the tunnel.
 16. The WTRU as in claim 15, wherein theaccess procedure is a session initiation protocol (SIP) registrationprocedure with the target system.
 17. The WTRU as in claim 15, whereinthe controller is further configured to authenticate the WTRU to thetarget system as part of the access procedure.
 18. The WTRU as in claim15, wherein the target system is a third generation partnership project(3GPP) system and the source system is a non-3GPP system.
 19. The WTRUof claim 15, wherein the access procedure is an attach procedure. 20.The WTRU as in claim 15, wherein the controller is further configured toestablish packet data protocol (PDP) context activation as part of theaccess procedure.
 21. The WTRU as in claim 15, wherein the controller isfurther configured to establish target system internet protocol (IP)connectivity as part of the access procedure.
 22. The WTRU as in claim15, wherein the first radio transceiver comprises a physical layercoupled by a crossover connection to at least one of a medium accesscontrol layer or a radio resource control layer of the second radiotransceiver to allow upper layers of the second radio transceiver toreceive target system information via the first radio transceiver. 23.The WTRU as in claim 15, wherein the tunnel is between the the secondradio transceiver and a Core Network of the target system using a radioconnection established by the first radio transceiver.